My company recently purchased a Nissan CYM02-003495 electric forklift with a dead battery. Had been sitting indoors for a few years. Replaced the battery and got it going and had to leave town for a few days right after. Our primary forklift driver reported that the brakes weren't working, i.e. "hey bossman, dem brakes ain't workin no more." It turned out that the brakes started getting a little bit soft but he never even thought to check the brake fluid level (he's as dumb as they come) so he used it until the master cylinder reservoir was nearly empty and the system was full of air. Fixed the leak, bled the system, and now the brake hydraulics work fine but there is no vacuum assist "power" brakes, just manual brakes like you are driving a car whose booster has failed. It seems like there is no vacuum going to the booster.

I know almost nothing about this forklift and it didn't come with a manual of any kind. Does anyone know where I can get a service/repair manual for it, either a download online or a hardcopy manual? Any idea what I should troubleshoot first, and how? TIA for any and all help.